Joint spacer

ABSTRACT

To change a spatial relationship between two or more bones in a patient&#39;s body, a wedge member is moved into a joint between the bones. As the wedge member enters the joint, pivotal movement occurs between the bones to change the orientation of the bones relative to each other. The wedge member may have a porous construction which enables bone to grow through the wedge member and immobilize the joint. The wedge member may be coated with and/or contain bone growth promoting material. The wedge member may be connected to only one of the bones or may be connected to two adjacent bones. If the wedge member is connected to only one bone, the joint may be capable of being flexed after the wedge member is inserted into the joint.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.10/163,480, filed on Jun. 5, 2002, now U.S. Pat. No. 7,780,670 which isa continuation of U.S. patent application Ser. No. 09/569,020, filed onMay 11, 2000, now U.S. Pat. No. 6,423,063, which is a continuation ofU.S. patent application Ser. No. 09/137,443, filed on Aug. 20, 1998, nowU.S. Pat. No. 6,099,531.

FIELD OF THE INVENTION

The present invention relates to a new and improved method of changing aspatial relationship between bones which are interconnected at a jointin a patient's body.

BACKGROUND OF THE INVENTION

It has previously been suggested that joints between bones be fused,that is, surgically immobilized, to promote patient comfort. Thus, U.S.Pat. No. 5,026,373 suggests that a fusion cage be positioned betweenadjacent vertebrae. Perforations are formed in the cage. The cage ispacked with a bone-inducing substance. A method for immobilizingvertebrae is also disclosed in U.S. Pat. No. 5,015,255.

It has previously been suggested that the spatial relationship betweenportions of a bone in a patient's body be changed to correctdeformities. This may be done by removing a wedge-shaped piece of bonein the manner disclosed in U.S. Pat. No. 5,601,565.

Another method of changing the spatial relationship between portions ofa bone in a patient's body includes forming a slot in the bone. A forkedwedge tool is inserted into the slot. A plate is then placed in acentral opening in the forked wedge tool and positioned against thebone. The plate is secured to the bone. The forked wedge tool is thenremoved from the opening. This method of changing the spatialrelationship between portions of a bone in a patient's body is disclosedin U.S. Pat. No. 5,620,448.

A method and apparatus for use in changing a spatial relationshipbetween portions of a bone in a patient's body is also disclosed inco-pending U.S. patent application Ser. No. 09/109,126, filed Jun. 30,1998 by Peter M. Bonutti and entitled Method And Apparatus For Use InOperating On A Bone. This application discloses the use of a wedgemember to expand a slot formed in a bone. The wedge member is porous andmay be coated with and/or contain bone growth promoting material. Thewedge member may have a configuration which corresponds to aconfiguration of a portion of the bone which is engaged by the wedgemember. Alternatively, the wedge member disclosed in the aforementionedapplication Ser. No. 09/109,126 may have a circular cross sectionalconfiguration with an external thread convolution to enable the wedgemember to be moved into an opening in a bone by rotating the wedgemember

SUMMARY OF THE INVENTION

A new and improved method and apparatus is provided to change a spatialrelationship between bones which are interconnected at a joint in apatient's body. When this is to be done, an opening is formed in aportion of the patient's body to expose the joint interconnecting thebones. One of the bones is moved relative to the other by expanding atleast a portion of the joint with a wedge member. The wedge member ismoved into the joint and applies force against the bones. The opening isclosed with the wedge member still disposed in the joint between thebones. Force is then transmitted between the bones through the wedgemember to maintain the joint in an expanded condition.

If the joint is to be flexed after being expanded by the wedge member,the wedge member may be connected with only one of the bones.Alternatively, if the joint is to be immobilized (fused) after insertingthe wedge member, the wedge member may be fixedly connected with thebones interconnected at the joint. The wedge member may be porous andmay be coated with and/or contain bone growth promoting material.

One embodiment of the wedge member has major side surfaces extendingbetween thick and thin end portions of the wedge member. The wedgemember is moved into the joint with the thin end portion leading. As thewedge member is moved into the joint, the thick trailing end portion ofthe wedge member expands the joint.

In another embodiment of the invention, the wedge member is rotatedrelative to the joint to expand the joint. The wedge member may have acircular cross sectional configuration and an external threadconvolution which extends from a thin leading end of the wedge member toa thick trailing end of the wedge member. The wedge member is pressedinto the joint and rotated to cause the wedge member to expand thejoint.

In another embodiment of the invention, the wedge member has surfaceareas which are relatively close together and other surface areas whichare relatively far apart. The wedge member is moved into the joint withthe surface areas which are close together engaging the adjacent bones.The wedge member is then rotated to apply force against the adjacentbones to expand the joint. The wedge member may be rotated about itscentral axis to apply forced against the bones and expand the joint.Alternatively, the wedge member may be rotated about a location wherethe wedge member engages one of the bones.

Regardless of which embodiment of the wedge member is selected, thewedge member may be used with any one of the many different bones andjoints in a patient's body. The wedge member may be utilized at jointsin a patient's wrist, ankle, hand, foot, back or other portions of thepatient's body. The wedge member may be particularly advantageous when ajoint between vertebrae in patient's back is to be immobilized. One ormore wedge members may be used to expand a joint and transmit forcebetween bones.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present invention will becomemore apparent from the following description taken in connection withthe accompanying drawings wherein:

FIG. 1 is a schematic illustration depicting the spatial relationshipbetween bones at a joint in a patient's body;

FIG. 2 is a schematic illustration depicting the manner in which a wedgemember is inserted into the joint between the bones of FIG. 1 to expanda portion of the joint and change the spatial relationship between thebones;

FIG. 3 is a schematic illustration of another embodiment of theinvention in which the joint of FIG. 1 is flexed after the wedge memberhas been inserted into the joint and connected with only one of thebones;

FIG. 4 is a schematic illustration depicting an alternative manner ofinserting the wedge member into the joint between the bones of FIG. 1;

FIG. 5 is a schematic pictorial illustration of the wedge member ofFIGS. 2 and 3;

FIG. 6 is a plan view further illustrating the construction of the wedgemember of FIG. 5;

FIG. 7 is a side view, taken generally along the line 7-7 of FIG. 6, ofthe wedge member of FIG. 5;

FIG. 8 is an enlarged fragmentary schematic sectional view depicting themanner in which the wedge member of FIGS. 5-7 is positioned, as shown inFIG. 2, in a joint between bones;

FIG. 9 is a fragmentary schematic sectional view, generally similar toFIG. 8, but on a reduced scale, illustrating an embodiment of theinvention in which the wedge member is porous;

FIG. 10 is a fragmentary schematic sectional view, generally similar toFIG. 9, illustrating an embodiment of the wedge member which is porousand has a chamber which holds bone growth promoting material;

FIG. 11 is a fragmentary schematic sectional view, generally similar toFIGS. 8-10, illustrating the manner in which the wedge member of FIG. 3is connected with only one bone to enable the joint between bones to beflexed;

FIG. 12 is a schematic illustration depicting the manner in which arotatable wedge member is moved into a joint between bones;

FIG. 13 is a schematic illustration depicting the wedge member of FIG.12 after the wedge member has been rotated to expand a portion of thejoint between the bones;

FIG. 14 is an enlarged fragmentary schematic sectional view, takengenerally along the line 14-14 of FIG. 12, illustrating the relationshipof the rotatable wedge member to the bones prior to rotation of thewedge member;

FIG. 15 is an enlarged fragmentary schematic sectional view, takengenerally along the line 15-15 of FIG. 13, illustrating the relationshipof the rotatable wedge member of FIG. 14 to the bones after rotation ofthe wedge member;

FIG. 16 is a fragmentary schematic sectional view, taken generally alongthe line 16-16 of FIG. 15, illustrating the manner in which therotatable wedge member is connected with the bones;

FIG. 17 is a fragmentary schematic sectional view, generally similar toFIG. 16, illustrating an embodiment of the rotatable wedge member whichis porous;

FIG. 18 is a fragmentary sectional view, generally similar to FIG. 14,illustrating the relationship between the bones at a joint when anotherembodiment of the rotatable wedge member is in the initial orientationillustrated in FIG. 12 relative to the bones;

FIG. 19 is a fragmentary schematic sectional view, generally similar toFIG. 15, illustrating the relationship of the rotatable wedge member ofFIG. 18 to the bones after the wedge member has been rotated;

FIG. 20 is a fragmentary schematic sectional view, taken generally alongthe line 20-20 of FIG. 19, further illustrating the construction of therotatable wedge member;

FIG. 21 is a schematic illustration, generally similar to FIG. 2,depicting the manner in which another embodiment of the rotatable wedgemember is moved into a joint between bones in a patient's body;

FIG. 22 is an enlarged schematic pictorial illustration of the rotatablewedge member of FIG. 21;

FIG. 23 is a fragmentary schematic illustration, generally similar toFIG. 2, depicting the manner in which another embodiment of the wedgemember is moved into a joint between bones in a patient's body; and FIG.24 is an enlarged fragmentary schematic sectional view, taken generallyalong the line 24-24 of FIG. 23, further illustrating the relationshipof the wedge member to the bones.

DETAILED DESCRIPTION OF THE INVENTION

General Description

An upper or first bone 30 in a patient's body is illustratedschematically in FIG. 1. A lower or second bone 32 is connected with theupper bone 30 at a joint 34. The bones 30 and 32 and joint 34 have beenillustrated schematically to represent any one of many bones and jointsin a patient's body. Thus, the bones 30 and 32 and joint 34 may bedisposed in a patient's hand, foot, back, or other portion of thepatient's body. It should be understood that the bones 30 and 32 andjoint 34 have been illustrated schematically in FIG. 1 as beingrepresentative of any one of the many joints in a human patient's bodyand it is not intended to limit the present invention to any particularjoint.

In order to correct deformities, improve patient comfort or otherreasons, it may be desired to change the spatial relationship betweenthe upper and lower bones 30 and 32. Thus, it may be desired to changethe angular relationship between longitudinal central axes 38 and 40from the relationship illustrated schematically in FIG. 1 to therelationship illustrated schematically in FIG. 2.

In order to change the spatial relationship between the longitudinalcentral axes 38 and 40 of the bones 30 and 32, an opening is formed in aportion of the patient's body to expose the joint 34. A wedge member 44(FIG. 2) is moved into the exposed joint 34 between the bones 30 and 32.The wedge member 44 applies force against the outer side surfaces of thebones 30 and 32 at the joint 34 to expand a portion of the joint.

As the wedge member 44 is moved into the joint 34, in the mannerillustrated schematically in FIG. 2, the lower bone 32 is pivotedrelative to the upper bone 30 about an axis extending through the joint34. This changes the angular orientation of the lower bone 32 relativeto the upper bone 30. Thus, the spatial relationship between the upperand lower bones 30 and 32 is changed from the spatial relationshipillustrated in FIG. 1 to the spatial relationship illustrated in FIG. 2by the wedge member 44.

In FIG. 2, the wedge member 44 has been illustrated schematically ashaving an extent which corresponds to approximately one-half of theextent of the joint 34. However, it is contemplated that the wedgemember 44 could have an extent which is either smaller than or greaterthan the extent illustrated in FIG. 2. Thus, the distance between thethick and thin end portions of the tapered wedge member 44 may be lessthan one-half of the width of the joint 34. Similarly, the distancebetween the thin leading end portion and thick trailing end portion ofthe wedge member 44 may be greater than one-half of the width of thejoint 34.

The wedge member 44 may be relatively narrow, as measured along the thinend portion of the wedge member. This would enable a plurality of narrowwedge members 44 to be used to expand a single joint 34. If the wedgemember 44 is relatively wide, only a single wedge member may be requiredto expand a joint 34, as shown in FIG. 2.

In the embodiment of the invention illustrated in FIG. 2, the joint 34is fused after the joint has been expanded by the wedge member 44 tochange the spatial relationship between the bones 30 and 32. Thus, afterthe joint 34 has been expanded by the wedge member 34, the joint isimmobilized with the upper and lower bones 30 and 32 in the spatialrelationship illustrated in FIG. 2. When the wedge member 44 is utilizedin association with joints between vertebrae in a patient's back, it isbelieved that it may be particularly advantageous to immobilize thejoint 34.

Immobilization of the joint 34 may be accomplished by connecting thewedge member 44 with both the upper bone 30 and the lower bone 32.Immobilization of the joint 34 may also be accomplished by the growth ofbone and/or other body tissue between the two bones 30 and 32 at thejoint 34. Known bone growth promoting materials may be provided at thejoint 34 if desired. The bone growth promoting materials may includebone morphogenic proteins and/or other osteoinductive materials.

In the embodiment of the invention illustrated in FIG. 3, the joint 34is capable of being flexed after the wedge member 44 has been utilizedto expand a portion of the joint. Thus, once the wedge member 44 hasbeen inserted into the joint 34, in the manner illustrated in FIG. 2,the patient may flex the joint under the influence of force transmittedto the bones 32 and 30 from muscle tissue in the patient's body.

When the joint 34 is flexed, as illustrated schematically in FIG. 3, thebone 32 moves away from the wedge member 44. The wedge member 44 isfixedly connected to only the bone 30. This allows the bone 32 to moveaway from the wedge member. It is believed that it will be particularlyadvantageous to enable the joint 34 to be flexed when the wedge memberis utilized to correct deformities occurring in hands, feet, wrists orankles of a patient. However, it should be understood that the wedgemember could be attached to a single bone at any joint in a patient'sbody which is to be flexed after the wedge member has been used toexpand the joint.

In the embodiment of the invention illustrated in FIGS. 1-3, the wedgemember 44 has been shown as being moved into the joint 34 in a directionwhich is perpendicular to an axis about which the joint is flexed. Thus,the wedge member 44 is moved into the joint 34 (FIG. 2) in a directionperpendicular to the axis about which the joint 34 is schematicallyillustrated in FIG. 3 as being flexed.

In the embodiment of the invention illustrated in FIG. 4, the wedgemember 44 is inserted into the joint 34 in a direction parallel to theaxis about which the joint is normally flexed. Thus, the wedge member 44is illustrated in FIG. 4 as being inserted into the joint 34 in adirection perpendicular to the plane of the drawing of the joint 34 inFIGS. 1 and 3. It should be understood that the wedge member 44 could beinserted into a joint, such as the joint 34, in any desired direction inorder to obtain a desired expansion of the joint. Thus, the wedge member44 could be moved into the joint 34 along a path which is neitherperpendicular to or parallel to the axis about which the joint isflexed.

After one or more wedge members 44 have been positioned in a joint 34,in the manner previously explained, the opening in the patient's body isclosed. When the opening in the patient's body is closed, the wedgemember 44 remains in the joint 34 between the bones 30 and 32. The wedgemember 44 is formed of a rigid material which is capable of transmittingforce between the bones 30 and 32 immediately after being positioned inthe joint 34. Therefore, the wedge member 44 is effective to maintainthe changed spatial relationship, such as the spatial relationshipillustrated in FIG. 2, between the bones 30 and 32 during loading of thejoint 34 immediately after positioning of the wedge member in the joint.

Wedge Member

The wedge member 44 (FIGS. 5-7) tapers from a thick end portion 50 to athin end portion 52. The wedge member 44 has flat upper and lower majorside surfaces 54 and 56 (FIG. 7) which slope toward each other from thethick end portion 50 to the thin end portion 52. The major side surfaces54 and 56 intersect at the thin end portion 52. The pointed thin endportion 52 of the wedge member 44 facilitates moving the wedge memberinto the joint 34 between the bones 30 and 32 (FIG. 2).

In the illustrated embodiment of the wedge member 44 (FIGS. 5-7), thethick end portion 50 has an outer side surface 60 which forms a portionof a cylinder. The thin end portion 52 extends diametrically across thecylinder (FIG. 6). Therefore, the wedge member 44 has a semi-circularconfiguration. However, it should be understood that the configurationof the upper and lower major side surfaces 54 and 56 of the wedge member44 corresponds to the configuration of the joint with which the wedgemember is to be associated.

The semi-circular outer side surface 60 will, for many joints at least,have an irregular configuration other than the semi-circularconfiguration illustrated in FIGS. 5 and 6. This enables the outer sidesurface 60 to be aligned with the outer side surfaces of the bones 30and 32 at the joint 34. Since most bones do not have outer side surfaceswhich form portions of a semi-circular, it is believed that in allprobability, the wedge member 44 will have an outer side surface 60 withan irregular configuration rather than the semi-circular configurationillustrated in FIG. 5.

The extent of the thin end portion 52 of the wedge member 44 may besubstantially less than shown in FIG. 6. Thus, the extent of the thinend portion 52 of the wedge member 44 may be less than one-half of theextent shown in FIG. 6. This would result in the major side surfaces 54and 56 of the wedge member 44 having a generally U-shaped configuration.Parallel triangular side surfaces would extend between the outer sidesurface 50 of the wedge member 44 and opposite ends of the thin endportion 52. These triangular side surfaces would be spaced from oppositesides of the joint 34 when the wedge member 44 is inserted into thejoint.

When the wedge member 44 has a relatively narrow, generally U-shapedconfiguration, a plurality of the wedge members may be inserted into asingle joint 34 (FIG. 1). When a plurality of narrow wedge members 44are used at one joint 34, the wedge members may have differentconfigurations. Thus, the wedge members 44 may have different lengthsand/or different angles between the upper and lower major side surfaces54 and 56 of the wedge members.

The upper and lower major side surfaces 54 and 56 of the wedge member 44slope toward each other from the thick end portion 50 to the thin endportion 52 of the wedge member. It is contemplated that a plurality ofwedge members 44 having different acute angles between the upper andlower major side surfaces 54 and 56 may be provided. This would enable asurgeon to select the wedge member 44 having a desired thickness at thethick end portion 50. Thus, if a surgeon determines that a joint shouldbe expanded to either a lesser or greater amount than would beaccomplished by a wedge member having one angle, the surgeon may selecta wedge member having a different angle and thickness to effect thedesired expansion of the joint 34. It is also contemplated that aplurality of wedge members 44 having different widths, as measured alongthe thin end portion 52, may be provided.

The acute angle between the flat upper and lower major side surfaces 54and 56 is determined by the extent to which the joint 34 is to beexpanded, that is, the extent to which the spatial relationship betweenthe bones 30 and 32 is to be changed by insertion of the wedge member44. Of course, the specific angle provided between the upper and lowermajor side surfaces 54 and 56 of the wedge member 44 will vary dependingupon the size of the joint with which the wedge member is used and theextent to which the spatial relationship between the bones 30 and 32 isto be changed by use of the wedge member. In addition, the length andwidth of the wedge member 44 inserted into a particular joint will bedetermined by the extent to which the joint is to be expanded and thetotal number of wedge members to be inserted into the joint.

It is believed that it may be desired to have the acute angle betweenthe upper and lower major side surfaces 54 and 56 (FIG. 6) of the wedgemember 44 within a range between one and thirty degrees. Although it isdifficult to be certain, it is believed that it may be preferred to havethe acute angle between the upper and lower major side surfaces 54 and56 of the wedge member 44 vary within a range of five degrees to twentydegrees. It should be understood that the foregoing specific ranges ofsizes for the angle between the upper and lower major side surfaces 54and 56 of the wedge member 44 have been set forth herein for purposes ofclarity of description and it is contemplated that the angle between theupper and lower major side surfaces 54 and 56 may be any one of manyangles other than these specific angles.

The size of the wedge member relative to a specific joint 34 may varydepending upon the deformity to be corrected. Thus, a narrow wedgemember 44 may have a thin end portion 52 (FIG. 6) with a length which isrelatively small compared to the width of a joint. The thin end portion52 of the narrow wedge member 44 could have a length of less than onefourth the distance across the joint. This would result in opposite endsof the thin end portion 52 being spaced from the periphery of the joint.It is contemplated that a plurality of narrow wedge members 44 could beused to expand a single joint.

The wedge member 44 may be formed of any one of many different knownmaterials which are compatible with a patient's body. For example, thewedge member may be formed of human or animal bone, stainless steel,tantalum, a porous ceramic, or a polymeric material. If desired, thewedge member may be formed of a biodegradable material. However, it ispreferred to have the wedge member 44 formed of a rigid material whichis capable of enabling force to be transmitted through the joint 34between the bones 30 and 32 immediately after installation of the wedgemember in the joint.

In the embodiment of the invention illustrated in FIG. 2, the joint 34is immobilized. To facilitate immobilization of the joint 34, the wedgemember 44 is fixedly connected with the bone 30 and with the bone 32. Tofacilitate fixedly connecting the wedge member 44 with the bones 30 and32, a pair of passages 64 and 66 are formed in the wedge member 44(FIGS. 6 and 7). When the wedge member 44 is positioned in the joint 34(FIG. 2), suitable fasteners, that is screws 70 and 72 extend throughthe passages 64 and 66 into the bones 30 and 32 in the manner indicatedschematically in FIG. 8. The screws 70 and 72 engage hard cortical outerlayers 76 and 78 of the bones 30 and 32. If desired, the screws 70 and72 could extend into the relatively soft cancellous bone 80 and 82.

Although the wedge member 44 has been illustrated in FIG. 8 as beingconnected with the bones 30 and 32 by a pair of screws 70 and 72, itshould be understood that the wedge member 44 may be connected with onlyone of the bones 30 or 32 by only one of the screws 70 or 72 if desired.For example, if the wedge member 44 is connected with the bone 30 by thescrew 70, the joint 34 could be flexed in the manner illustratedschematically in FIG. 3, after the wedge member 44 has been moved intothe joint.

Positioning of Wedge Member

When the wedge member 44 is to be inserted in to the joint 34 to changethe spatial relationship between the bones 30 and 32 in the mannerillustrated schematically in FIG. 2, a location for insertion of thewedge member into the joint 34 is selected by a surgeon. The specificlocation at which the wedge member 44 is inserted into the joint 34 toexpand the joint will be selected by the surgeon as a function of thedesired result from a particular operation. In addition, the size of thewedge member 44 will be selected by the surgeon as a function of thejoint and the result to be obtained from a particular operation.

The configuration of the wedge member 44 will be selected by the surgeonas a function of the location where the wedge member is to be insertedinto the joint 34. The wedge member 44 may be relatively wide and have along thin end portion 52, as shown in FIG. 6, to enable the thin endportion to extend between opposite sides of the joint. Alternatively,the wedge member 44 may be relatively narrow and have a thin end portion52 which is short. If this is done, the thin end portion 52 would notextend between opposite sides of the joint 34. A plurality of the narrowwedge members 44 may be inserted into a single joint 34 to expand thejoint and transmit force between the bones 30 and 32.

The surgeon makes an incision in soft body tissue surrounding the joint34 to expose the joint. Once the joint 34 has been exposed, the thin endportion 52 (FIGS. 5 and 6) of the wedge member 44 is moved into thejoint 34. When the wedge member 44 is to be inserted into a joint in themanner illustrated schematically in FIG. 2, the longitudinal centralaxis of the thin end portion 52 of the wedge member is aligned with anaxis about which the joint pivots. The wedge member is then moved intothe joint 34 along a linear path which extends perpendicular to the axisabout which the joint pivots. The wedge member 44 is moved into thejoint 34 by applying force against the trailing thick end portion 50 ofthe wedge member.

As the wedge member 44 is moved into the joint 34, the upper major sidesurface 54 (FIGS. 5 and 7) of the wedge member slides along an outerside surface 88 (FIG. 8) of the outer layer 76 of hard cortical bone.The lower major side surface 56 of the wedge member 44 slides along anouter side surface 90 of the outer layer 78 of hard cortical bone.

The outer side surfaces 88 and 90 of the bones 30 and 32 are in theirnaturally occurring conditions. Thus, the outer side surfaces 88 and 90of the bones 30 and 32 are not cut away to prepare for insertion of thewedge member 44 into the joint 34. However, it should be understood thatunder certain circumstances that it may be necessary to abrade orotherwise cut the outer side surfaces 88 and 90 of the outer layers 76and 78 of hard cortical bone to prepare the joint 34 for insertion ofthe wedge member 44.

As the thin leading end portion 52 (FIG. 8) of the wedge member 44 movesinto the joint 34, the upper and lower major side surfaces 54 and 56apply force against the outer side surfaces 88 and 90 on the bones 30and 32. As this occurs, the joint 34 is expanded. As the joint 34 isexpanded, the bone 32 is pivoted, relative to the bone 30, from theinitial orientation, shown in FIG. 1, to the improved orientation shownin FIG. 2. As this occurs, the longitudinal central axis 40 of the bone32 moves relative to the longitudinal central axis 38 of the bone 30.Therefore, the angular relationship between the bones 30 and 32 ischanged by expansion of a portion of the joint 34 by insertion of thewedge member 44 into the joint.

When the wedge member 44 has been pressed the desired distance into thejoint 34, by the application of force against the thick end portion 50of the wedge member 44, the outer side surface 60 on the wedge membermoves slightly inward of the outer side surfaces on the bones 30 and 32(FIG. 8). The outer side surface 60 on the wedge member 44 has aconfiguration which corresponds to the configurations of the outer sidesurfaces on the bones 30 and 32 adjacent to the joint 34. Therefore, thewedge member 44 does not project outward from the joint. This minimizesany tendency of the wedge member to subsequently abrade body tissueadjacent to the joint 34.

Once the wedge member 44 has been moved into the desired orientationrelative to the bones 30 and 32, as illustrated schematically in FIG. 8,the wedge member 44 is fixedly connected with the bones 30 and 32 by thescrews 70 and 72 to immobilize the joint. The area surrounding anddirectly adjacent to the wedge member 44 is packed with bone growthpromoting material and/or bone chips. The bone growth promotingmaterials may include bone morphogenic proteins and/or otherosteoinductive materials. This promotes fusion of the bones 30 and 32for remedial immobilization of the joint 34.

Since the wedge member 44 is rigid, it can immediately transmit loadsbetween the bones 30 and 32. Therefore, after the incision which exposedthe joint 34 has been closed, the patient can begin to load the joint34. The wedge member 44 is effective to maintain the joint 34 in anexpanded condition during loading of the joint. Therefore, the bones 30and 32 remain in the improved spatial relationship illustrated in FIG. 2during loading of the joint 34.

Wedge Member—Second Embodiment

In the embodiment of the invention illustrated in FIGS. 1-8, a solidwedge member has been utilized to expand the joint 34. In the embodimentof the invention illustrated in FIG. 9, a porous wedge member isutilized to expand a joint. Since the embodiment of the inventionillustrated in FIG. 9 is generally similar to the embodiment of theinvention illustrated in FIGS. 1-8, similar numerals will be utilized todesignate similar components, the suffix letter “a” being associatedwith the numerals of FIG. 9 in order to avoid confusion.

A wedge member 44 a is positioned in a joint 34 a between bones 30 a and32 a. The wedge member 44 a engages outer side surfaces 88 a and 90 a onlayers 76 a and 78 a of hard cortical bone. The outer side surfaces 88 aand 90 a are in their naturally occurring conditions.

As the wedge member 44 a is moved into the joint 34 a, flat upper andlower major side surfaces 54 a and 56 a on the wedge member 44 a slidealong the outer side surfaces 88 a and 90 a on the bones 30 a and 32 a.The upper and lower major side surfaces 54 a and 56 a of the wedge 44 aapply force against the outer side surfaces 88 a and 90 a of the bones30 a and 32 a to expand the joint 34 a as the wedge member is moved intothe joint. The wedge member 44 a is moved into the joint 34 a under theinfluence of force applied against an outer side surface 60 a on atrailing thick end portion 50 a of the wedge member 44 a.

Once the joint 34 a has been expanded to change the spatial relationshipbetween the bones 30 a and 32 a, suitable fasteners (screws) 70 a and 72a are inserted through passages in the wedge member 44 a. The screws 70a and 72 a engage the hard cortical outer layers 76 a and 78 a of boneto fixedly secure the wedge member 44 a with the bones 30 a and 32 a.With further reference to FIGS.8-9, it may be seen that passage 64widens proximate end portion 50 a configured to receive a head offastener 70 a that is wider than a shaft of the fastener.

A single wedge member 44 a is used to expand the joint 34 a. However, aplurality of narrow wedge members 44 a may be inserted into the joint atspaced apart locations about the periphery of the joint if desired.

In accordance with a feature of this embodiment of the invention, thewedge member 44 a is porous so that bone can grow through the wedgemember. It is contemplated that the wedge member could be provided witha porous construction by having passages extend through the wedge memberbetween the upper and lower major side surfaces 54 a and 56 a of thewedge member. The open ends of the passages would enable bone to growthrough the wedge member 44 a.

In the embodiment of the wedge member 44 a illustrated in FIG. 9, thewedge member is formed of a rigid open cell material. The open cellmaterial provides cavities in which bone can grow through the wedgemember 44 a. Thus, the wedge member 44 a (FIG. 9) has a cellularconstruction similar to coral.

It is contemplated that the wedge member 44 a may be coated with amaterial which promotes the growth of bone. The cells in the wedgemember 44 a may be at least partially filled with bone growth promotingmaterial. The bone growth promoting materials may be bone morphogenicproteins and other osteoinductive materials. In addition to bone growthpromoting material associated with the wedge member 44 a, the spacearound and adjacent to the wedge member 44 a in the joint 34 a may bepacked with bone growth promoting material and/or bone chips.

The wedge member 44 a is rigid and can be subject to normal loadingimmediately after being positioned in the joint 34 a. This enables thepatient to subject the bones 30 a and 32 a to normal loading withoutwaiting for fusion to occur through and around the wedge member 44 a. Ofcourse, with the passage of time, the growth of bone through the wedgemember 44 a and around the wedge member will strengthen theimmobilization of the joint 34 a.

In the embodiment of the invention illustrated in FIG. 9, the passagesthrough the wedge member 44 a are formed by the open cell structure ofthe wedge member This results in the passages through the wedge member44 a having an irregular configuration. If desired, linear passagescould be formed in the wedge member 44 a. The linear passages may bedrilled, cast, or formed in other ways in the wedge member 44 a.

Hollow Wedge Member

In the embodiment of the invention illustrated in FIGS. 1-8, the wedgemember 44 is formed by a solid piece of material. In the embodiment ofthe invention illustrated in FIG. 9, the wedge member 44 a is formed bya continuous piece of porous material. In the embodiment of theinvention illustrated in FIG. 10, the wedge member is formed by a hollowpiece of porous material. Since the embodiment of the inventionillustrated in FIG. 10 is generally similar to the embodiments of theinvention illustrated in FIGS. 1-9, similar numerals will be utilized todesignate similar components, the suffix letter “b” being associatedwith the numerals of FIG. 10 to avoid confusion.

In the embodiment of the invention illustrated in FIG. 10, a wedgemember 44 b is inserted into a joint 34 b between bones 30 b and 32 b toexpand the joint. Expansion of the joint 34 b by the wedge member 44 bchanges the spatial relationship between the bones 30 b and 32 b. Thewedge member 44 b is held against movement relative to the bones 30 band 32 b by fasteners (screws) 70 b and 72 b. The fasteners 70 b and 72b extend through passages in the wedge member 44 b into layers 76 b and78 b of hard cortical bone on bones 30 b, 32 b. The layers 76 b and 78 bare in their naturally occurring condition.

When the wedge member 44 b is to be moved into the joint, a thin endportion 52 b of the wedge member 44 b is pressed into the joint 34 b byapplying force against an outer side surface 60 b at a thick end portion50 b of the wedge member 44 b. The force applied against the trailingthick end portion 50 b of the wedge member 44 b causes flat upper andlower major side surfaces 54 b and 56 b to slide along outer sidesurfaces 88 b and 90 b. As the upper and lower major side surfaces 54 band 56 b on the wedge member 44 b slide along the outer side surfaces 88b and 90 b of the bones 30 b and 32 b, the wedge member applies forceagainst the bones to expand the joint 34 b in the manner previouslyexplained.

In accordance with a feature of this embodiment of the invention, thewedge member 44 b (FIG. 10) is hollow. Therefore, a compartment orcavity 100 is formed in the wedge member 44 b. The compartment 100 hasupper and lower inner side surfaces 102 and 104 which are smaller thanthe upper and lower major side surfaces 54 b and 56 b of the wedgemember 44 b. However, the inner side surfaces 102 and 104 of thecompartment 100 have the same general configuration as the upper andlower major side surfaces 54 b and 56 b of the wedge member 44 b.

The compartment 100 is filled with bone growth inducing material 110.The bone growth inducing material 110 is positioned in the compartment100 through a suitable opening (not shown) formed in either the uppermajor side surface 54 b or the lower major side surface 56 b of thewedge member 44 b. Once the compartment 100 has been filled with bonegrowth inducing material 110, the opening to the compartment is closed.However, the wedge member 44 b is formed of a porous material whichenables bone to grow through the wedge member.

The growth of bone through the wedge member 44 b is promoted by the bonegrowth inducing material 110 in the compartment 100. The bone growthinducing material 110 in the compartment 100 may be any of many knownbone morphogenic proteins and osteoinductive materials. For example,apatite compositions with collagen may be utilized. Demineralized bonepowder may also be utilized. Regardless of which of the known bonegrowth inducing materials are selected, the presence of the bone growthpromoting material 110 in the compartment 100 will promote a growth ofbone through openings in the porous wedge member 44 b.

The wedge member 44 b may, itself, be formed of a suitable rigidmaterial, such as tantalum, stainless steel, or ceramic materials. Inaddition to the bone growth inducing material 110, the surfaces of thewedge member 44 b and openings in the porous material of the wedgemember may be coated with suitable bone growth promoting materials.

The wedge member 44 b is porous so that bone can grow through the wedgemember. In the embodiment of the invention illustrated in FIG. 10, thewedge member is formed of an open cell material having a constructionsimilar to coral. The open cell material provides irregular passageswhich extend through the wedge member 44 b and enable the bone to growthrough the wedge member. However, it should be understood that thewedge member 44 b could be formed of a solid material with passagesdrilled or cast in the wedge member. Regardless of which of thematerials the wedge member is formed, it is believed that it will beadvantageous to have the material be sufficiently rigid to enable thejoint 44 b to be load bearing immediately after an operation installingthe wedge member in the joint.

Single Connection for Wedge Member

In the embodiments of the invention illustrated in FIGS. 8-10, the wedgemembers 44, 44 a, and 44 b are connected with bones on opposite sides ofa joint by suitable fasteners (screws). In the embodiment of theinvention illustrated in FIG. 11, the wedge member is connected withonly one of the bones. Since the embodiment of the invention illustratedin FIG. 11 is generally similar to the embodiments of the inventionillustrated in FIGS. 1-10, similar numerals will be utilized todesignate similar components, the suffix letter “c” being associatedwith the numerals of FIG. 11 to avoid confusion.

A wedge member 44 c is inserted into a joint 34 c between upper andlower bones 30 c and 32 c. The wedge member 44 c has the same generalconfiguration and construction as the wedge member 44 of FIGS. 5-8.However, the wedge member 44 c is connected with only one of the bones30 c and 32 c. Thus, rather than utilizing a pair of fasteners to securethe wedge member 44 c to the upper and lower bones 30 c and 32 c, only asingle fastener 70 c is utilized to connect the wedge member 44 c withthe upper bone 30 c. Therefore, installation of the wedge member 44 c inthe joint 34 c does not result in immobilization of the joint.

Since the wedge member 44 c is connected with the bone 30 c by thefastener 70 c, the bone 32 c may be moved away from the wedge memberduring flexing of the joint 34 c. This may result in the upper majorside surface 54 c on the wedge member 54 c remaining in engagement withthe outer side surface 88 c on the bone 30 c while the outer sidesurface 90 c on the bone 32 c moves away from the lower major sidesurface 56 c on the wedge member 44 c. Of course, a single fastener 70 cmay be utilized to hold the wedge member in the joint 34 c where theouter side surfaces 88 c and 90 c on the upper and lower bones 30 c and32 c remain in engagement with the upper and lower major side surfaces54 c and 56 c of the wedge member 44 c.

In the embodiment of the wedge member 44 c illustrated in FIG. 11, thewedge member is formed of a solid material through which bone does notgrow. However, it is contemplated that a single fastener, correspondingto the fastener 70 c of FIG. 11, may be used to connect a porous wedgemember with a bone. Of course, bone may grow through the porous wedgemember. The porous wedge member may have the same construction as shownin FIGS. 9 and 10, with the exception of being held in place by only asingle fastener 70 c.

Rotatable Wedge Member

In the embodiment of the invention illustrated in FIGS. 1-11, the wedgemember 44 is moved into the joint 34 between the upper and lower bones30 and 32 along a linear path. The wedge member 44 is moved into thejoint 34 with the thin end portion 52 of the wedge member leading andthe thick end portion 50 of the wedge member trailing. The taperedconfiguration of the wedge member results in the application of forceagainst the upper and lower bones 30 and 32 to expand the joint 34 inthe manner previously explained.

In the embodiment of the invention illustrated in FIGS. 12-16, the wedgemember is moved into the joint between the upper and lower bones andthen rotated. During initial movement of the wedge member into the jointbetween the bones, there may be some expansion of the joint. Duringrotation of the wedge member in the joint, there is further expansion ofthe joint. Since the embodiment of the invention illustrated in FIGS.12-15 is generally similar to the embodiments of the inventionillustrated in FIGS. 1 -11, similar numerals will be utilized todesignate similar components, the suffix letter “d” being associatedwith the numerals of FIGS. 12-15 to avoid confusion.

Upper and lower bones 30 d and 32 d are interconnected at a joint 34 d(FIG. 12). Prior to insertion of a wedge member 44 d, the upper andlower bones 30 d and 32 d are in the same spatial orientation relativeto each other as is illustrated in FIG. 1. Upon insertion of the wedgemember 44 d into the joint 34 d, in the manner illustrated in FIG. 12,there may be a slight expansion of the joint 34 d and a slight change inthe orientation of the upper bone 30 d relative to the lower bone 32 d.There is a relatively small change in the spatial relationship betweenthe upper bone 30 d and the lower bone 32 d because the wedge member 44d is inserted into the joint 34 d in an orientation in which the wedgemember 44 d is relatively thin as viewed in FIG. 12, that is, in adirection transverse to the joint 34 d.

After the wedge member 44 d has been inserted into the joint 34 d in themanner indicated schematically in FIG. 12, the wedge member 44 d isrotated, through less than one revolution, about an axis 120 in themanner indicated schematically by an arrow 122 in FIG. 13. As the wedgemember 44 d is rotated through approximately ninety degrees about theaxis 120, the wedge member applies force against the upper and lowerbones 30 d and 32 d to expand the joint 34 d. As the joint 34 d isexpanded by rotation of the wedge member 44 d, the spatial relationshipbetween the upper and lower bones 30 d and 32 d changes from the spatialrelationship illustrated schematically in FIG. 12 to the spatialrelationship illustrated schematically in FIG. 13. Thus, by the combinedeffect of insertion of the wedge member 44 d into the joint 34 d androtation of the wedge member in the joint, the spatial relationship ofthe upper and lower bones 30 d and 32 d was changed from the spatialrelationship illustrated in FIG. 1 for the bones 30 and 32 to thespatial relationship illustrated in FIG. 13 for the upper and lowerbones 30 d and 32 d.

The bones 30 d and 32 d illustrated schematically in FIGS. 12 and 13should be considered as being representative of bones at many differentlocations in a patient's body. Thus, the bones 30 d and 32 d may be anyof the many bones in a patient's wrist, ankle, hand, foot, back, orother portion of a patient's body. The bones 30 d and 32 d may bevertebrae in a patient's back. It should be understood that the wedgemember 44 d may be used with any one of the many different types ofjoints in a patient's body.

The wedge member 44 d has a generally oval, cross-sectionalconfiguration (FIGS. 14 and 15), as viewed in a plane perpendicular to alongitudinal central axis of the wedge member. Thus, the wedge member 44d has an outer side surface 126 (FIG. 14) with a pair of arcuate noseportions 128 and 130. The arcuate nose portions 128 and 130 of the outerside surface 126 are interconnected by a pair of arcuate side portions134 and 136.

The arcuate outer side surface 126 tapers from a thick end portion 50 d(FIG. 16) to a thin end portion 52 d. In the illustrated embodiment ofthe wedge member 44 d, the thin end portion 52 d is blunt or truncated.Thus, the thin end portion 52 d of the wedge member 44 d does not cometo a sharp point as does the thin end portions of the wedge members 44,44 a, 44 b and 44 c.

It should be understood that the wedge members 44 a, 44 b and 44 c(FIGS. 5-11) could be constructed with a blunt thin end portioncorresponding to the blunt thin end portion 52 d (FIG. 16) on the wedgemember 44 d if desired. However, it is believed that by having the thinend portion of the wedge members of FIGS. 5-11 taper to a sharp point,insertion of the wedge members into a joint is facilitated. Similarly,if desired, the wedge member 44 d could be provided with a thin endportion 52 d (FIG. 16) which comes to a sharp point in the same manneras the wedge members 44, 44 a, 44 b and 44 c.

When the wedge member 44 d is inserted into the joint 34 d (FIG. 14),the arcuate side portion 134 engages the outer side surface 88 d of theupper bone 30 d and the arcuate side portion 136 engages the outer sidesurface 90 d of the lower bone 32 d. The arcuate side portions 134 and136 are relatively close together so that minimal expansion of the joint34 d occurs when the wedge member 44 d is inserted into the joint. Asthe wedge member 44 d is inserted into the joint 34 d, the arcuate sideportions 134 and 136 slide along and are effective to apply forceagainst the outer side surfaces 88 d and 90 d of the upper and lowerbones 30 d and 32 d to effect some expansion of the joint 34 d. Theouter side surfaces 88 d and 90 d of the bones 30 d and 32 d are intheir naturally occurring conditions.

After the wedge member 44 d has been inserted into the joint 34 d, inthe manner shown in FIGS. 12 and 14, a suitable tool is inserted into ahexagonal socket 140 (FIG. 14) in the wedge member 44 d. Torque istransmitted from the tool to the wedge member 44 d to rotate the wedgemember through less than one revolution in the direction indicated bythe arrow 122 in FIGS. 13 and 15. This results in the wedge member 44 dbeing rotated through approximately ninety degrees in a clockwisedirection from the position shown in FIG. 14 to the position shown inFIG. 15. As the wedge member 44 d is rotated, the wedge member appliesforce against the upper and lower bones 30 d and 32 d and expands thejoint 34 d.

Upon initiation of rotation of the wedge member 44 d from the positionshown in FIG. 14 toward the position shown in FIG. 15, the arcuate sideportions 134 and 136 slide along the outer side surfaces 88 d and 90 don the bones. As the rotation of the wedge member 44 d continues, thearcuate nose portions 128 and 130 of the wedge member 44 d approach theouter side surfaces 88 d and 90 d of the upper and lower bones 30 d and32 d. As this is occurring, the joint 34 d is expanded by the forceapplied against the upper and lower bones 30 d and 32 d by the wedgemember 44 d. When the wedge member 44 d reaches the position shown inFIG. 15, the arcuate nose portions 128 and 130 engage the outer sidesurfaces 88 d and 90 d on the upper and lower bones 30 d and 32 d tohold the joint 34 d in the expanded condition illustrated in FIGS. 15and 16.

A pair of mounting tabs 144 and 146 (FIG. 16) are integrally formed withthe wedge member 44 d. The mounting tabs 144 and 146 project outwardlyfrom the end portion 50 d of the wedge member 44 d. The mounting tabs144 and 146 are aligned with the arcuate nose portions 128 and 130 ofthe outer side surface 126 on the wedge member 44 d. Therefore, themounting tabs 144 and 146 are disposed adjacent to the bones 30 d and 32d in the manner illustrated schematically in FIG. 16.

A pair of retaining screws 70 d and 72 d extend through the mountingtabs 144 and 146 into the outer layers 76 d and 78 d of hard cancellousbone on the upper and lower bones 30 d and 32 d. The mounting screws orfasteners 70 d and 72 d are effective to hold the wedge member 44 dagainst rotation relative to the upper and lower bones 30 d and 32 d.Bone growth promoting material and/or bone chips may be packed in thejoint 34 d around the wedge member 44 d. The wedge member 44 d is rigidand can transmit force between the bones 30 d and 32 d as soon as it isrotated to the position shown in FIGS. 15 and 16.

As is perhaps best seen in FIG. 15, the wedge member 44 d is narrowerthan the distance across the joint 34 d. Therefore, a plurality of wedgemembers 44 d may be utilized to hold the joint 34 d in the expandedcondition of FIGS. 15 and 16. The plurality of wedge members 44 d couldbe positioned in the joint 34 d with their rotational axes 120 (FIG. 16)in a parallel relationship or with their rotational axes 120 skewedrelative to each other. If a plurality of wedge members 44 d areutilized, they could be of different sizes or have different angles oftaper along the axis 120.

It should be understood that the wedge members 44, 44 a, 44 b and 44 cof FIGS. 5-11 could also be relatively narrow. A plurality of wedgemembers of FIGS. 5-11 could be positioned in a joint with theirlongitudinal axes either parallel or skewed relative to each other.

Porous Rotatable Wedge Member

In the embodiment of the invention illustrated in FIGS. 12-16, the wedgemember 44 d is formed as a solid body of rigid material, such asstainless steel. The wedge member in the embodiment of the inventionillustrated in FIG. 17 is formed of a rigid porous material. Since theembodiment of the invention illustrated in FIG. 17 is generally similarto the embodiments of the invention illustrated in FIGS. 1-16, similarnumerals will be utilized to designate similar components, the suffixletter “e” being associated with the numerals of FIG. 17 to avoidconfusion.

The wedge member 44 e is disposed in a joint 34 e between upper andlower bones 30 e and 32 e. The wedge member 44 e applies force againstthe outer side surfaces 88 e and 90 e of the upper and lower bones 30 eand 32 e to expand the joint 34 e and change the orientation of theupper and lower bones relative to each other. In the embodiment of theinvention illustrated in FIG. 17, the wedge member 44 e tapers from athick end portion 50 e to a thin end portion 52 e. In the illustratedembodiment of the invention, the thin end portion 52 e of the wedgemember 44 e has a pointed configuration rather than the bluntconfiguration of the wedge member 44 d of FIG. 16. However, the wedgemember 44 e could have the same configuration as the wedge member 44 dif desired.

The wedge member 44 e (FIG. 17) has an oval cross sectionalconfiguration, as viewed on a plane extending perpendicular to a centralaxis 120 e of the wedge member 44 e. Thus, the wedge ember 44 e has anouter side surface 126 e with arcuate nose portions 128 e and 130 e. Thearcuate nose portions 128 e and 130 are interconnected by arcuate sideportions corresponding to the arcuate side portions 134 and 136 of thewedge member 44 d (FIGS. 14 and 15). A socket 140 e (FIG. 17) isprovided in the wedge member 44 e to facilitate the application oftorque to the wedge member.

In accordance with a feature of the embodiment of the inventionillustrated in FIG. 17, the wedge member 44 e is formed of a rigidporous material having an open cell construction. The porous open cellconstruction of the wedge member 44 e enables bone to grow through thewedge member. The wedge member 44 e may have an open cell constructionsimilar to the construction of coral.

The wedge member 44 e may be coated with bone growth promoting materialsto promote the growth of bone through the wedge member. The open cellsin the porous wedge member 44 e could be at least partially filled withthe bone growth promoting material. In addition, bone growth materialsand/or bone chips may be packed in the joint 34 e around the wedgemember 44 e. The bone growth promoting materials may include bonemorphogenic proteins and/or other osteoinductive materials.

A pair of fasteners 70 e and 72 e are provided to connect the wedgemember 44 e with the upper and lower bones 30 e and 32 e. Thus, thefasteners 70 e extends into the outer layer 76 e of hard cortical boneon the upper bone 30 e. Similarly, the fastener 72 e extends into theouter layer 78 e of hard cortical bone on the lower bone 32 e. In theillustrated embodiment of the invention, the fasteners 70 e and 72 eextend through passages in the wedge member 44 e into the upper andlower bones 30 e and 32 e. However, if desired, the wedge member 44 ecould be provided with mounting tabs, similar to the mounting tabs 144and 146 of FIG. 16.

When the wedge member 44 e is to be used to change the spatialrelationship between the upper and lower bones 30 e and 32 e, the wedgemember is inserted into the joint 34 e with the arcuate nose portions128 e and 130 e of the wedge member spaced from the outer side surfaces88 e and 90 e on the upper and lower bones 30 eand 32 e. At this time,the wedge member 44 e is in the same orientation as is illustrated inFIG. 14 for the wedge member 44 d. Arcuate side portions of the arcuateouter side surface 126 e on the wedge member 44 e engage the outer sidesurfaces 88 e and 90 e on the upper and lower bones 30 e and 32 e in thesame manner as is illustrated for the wedge member 44 d in FIG. 14.

Although inserting the wedge member 44 e into the joint 32 e may effectan initial, relatively small expansion of the joint, the majority of theexpansion of the joint 34 e is obtained by rotating the wedge member 44e about its central axis 120 e. To rotate the wedge member 44 e aboutits central axis 120 e, a suitable tool is inserted into the socket 140e. Force is transmitted from the tool to the wedge member 44 e to rotatethe wedge member. As the wedge member is rotated relative to the upperand lower bones 30 e and 32 e, the wedge member further expands thejoint 34 e and effects further change in the spatial relationshipbetween the upper and lower bones 30 e and 32 e.

Once the wedge member 44 e has been moved to the position illustrated inFIG. 17, that is, to a position corresponding to the position of thewedge member 44 d in FIG. 15, the wedge member is connected to the upperand lower bones 30 e and 32 e. To connect the wedge member with theupper and lower bones 30 e and 32 e, the screws 70 e and 72 e areinserted through passages in the wedge member into the bone. Bone growthpromoting material and/or bone chips may be packed in the joint 34 earound the wedge member 44 e.

Although a single wedge member 44 e is utilized to expand the joint 34e, a plurality of wedge members could be utilized if desired. When aplurality of wedge members 34 e are held to expand the joint 34 e, thewedge members may all be of the same size and configuration or may havedifferent sizes and configurations.

Rotatable Wedge Member Alternative—Embodiment

The wedge members 44 d and 44 e are rotated about their central axes 120d and 120 e (FIGS. 16 and 17) to effect expansion of the joints 34 d and34 e. In the embodiment of the invention illustrated in FIGS. 18 through20, the wedge member is rotated about a location where the wedge memberengages one of the bones. Since the embodiment of the inventionillustrated in FIGS. 18-20 is generally similar to the embodiments ofthe invention illustrated in FIGS. 1-17, similar numerals will beutilized to designate similar components, the suffix letter “f” beingassociated with the numerals of FIGS. 18-20 to avoid confusion.

Upper and lower bones 30 f and 32 f are interconnected at a joint 34 f.A wedge member 44 f is illustrated inserted into the joint 34 f betweenthe upper and lower bones 30 f and 32. The wedge member 44 f ispositioned in the joint 34 f (FIG. 18) with a relatively narrow width ofthe wedge member between outer side surfaces 88 f and 90 f on hardcortical outer layers 76 f and 78 f of the upper and lower bones 30 fand 32 f. Although the outer side surfaces 88 f and 90 f of the upperand lower bones 30 f and 32 f are in their naturally occurringconditions, it is contemplated that a surgeon may want to prepare thesurfaces of the bone for the wedge member 44 f by cutting awayextraneous material to promote seating of the wedge member 44 f on theupper and lower bones 30 f and 32 f.

The wedge member 44 f has an arcuate nose portion 128 f and a pivot endportion 150 f. The nose portion 128 f and pivot end portion 150 f areinterconnected by side portions 134 f and 136 f. The side portion 134 fhas a continuously curving arcuate configuration. The side portion 136 fmay have a linear configuration.

The side portion 136 f has a relatively flat area which engages theouter side surface 90 f on the lower bone 32 f when the wedge member 44f is oriented as illustrated in FIG. 18 If desired, the side portion 136f could have an arcuate configuration corresponding to the arcuateconfiguration of the side portion 134 f. If the side portion 136 f hadthe same configuration as the side portion 134 f, the wedge member 44 fwould have a symmetrical configuration about an axis extending throughthe relatively sharply defined pivot end portion 150 c.

The wedge member 44 f has the same size and configuration throughout itslength. Thus, the end portion 150 f of the wedge member is the same sizeas the end portion 52 f (FIG. 20). However, if desired, the wedge member44 f could taper from a relatively thick end portion 50 f to arelatively thin or small end portion 52 f in the manner illustrated inFIGS. 16 and 17 for the wedge members 44 d and 44 e. It should beunderstood that any one of the wedge members illustrated in FIGS. 1through 17 could be formed with the same configuration as the wedgemember 44 f if desired. However, it is believed that in most instancesit will probably be preferred to provide the wedge members of FIGS. 1-17with an axially tapered configuration to facilitate insertion of thewedge members into the joint between the upper and lower bones.

The wedge member 44 f (FIGS. 18, 19 and 20) is formed of a rigid porousopen cell material. The rigid porous open cell material of the wedgemember 44 f has a construction generally similar to coral. However, thewedge member 44 f could be formed of a nonporous material if desired.

It is contemplated that the wedge member 44 f, like the wedge membersillustrated in FIGS. 1-17, may be formed of human or animal bone, metal,ceramic, or a polymeric material. While it may be preferred to form thewedge member 44 f of a porous material to enable bone to grow throughthe wedge member, the wedge member 44 f may be formed of a solidmaterial through which bone can not grow.

The wedge member 44 f may be coated with or packed with bone growthpromoting materials. The bone growth promoting materials may be bonemorphogenic proteins and/or other osteoinductive materials. Bone chipsmay be included with the bone morphogenic proteins and/or otherosteoinductive materials packed around the wedge member 44 f.

Of course, the wedge member 44 f may be provided with a taperedconfiguration to facilitate insertion into the joint 34 f. When thewedge member 44 f is to be utilized to change the spatial relationshipbetween the upper and lower bones 30 f and 32 f, the wedge member isinserted into the joint 34 f. The illustrated embodiment of the wedgemember 44 f has the same size and configuration throughout its length.Therefore, the wedge member 44 f does not taper to a thin end portion tofacilitate insertion of the wedge member into the joint 34 f. Therefore,the joint 34 f may be initially expanded with a suitable tool to enablethe wedge member 44 f to be inserted into the joint, in the orientationillustrated in FIG. 18.

When the wedge member 44 f is inserted into the joint 34 f, there willbe a slight initial expansion of the joint. As was previously mentioned,the wedge member 44 f may have an axially tapered configuration, similarto the configuration of the wedge members 44 d and 44 e (FIGS. 16 and17), to facilitate insertion of the wedge member 44 f into the joint 34f.

As the wedge member 44 f is initially inserted into the joint 34 f, theside portions 1 34 f and 136 f on the wedge member 44 f slide along theouter side surfaces 88 f and 90 f on the upper and lower bones 30 f and32 f. At this time, the arcuate nose portion 128 f of the wedge member44 f is spaced from the outer side surface surfaces 88 f and 90 f of theupper and lower bones 30 f and 32 f.

To further change the spatial relationship between the upper and lowerbones 30 f and 32 f, the wedge member 44 f is rotated about an axisextending through a location where the pivot end portion 150 f of thewedge member 44 f engages the outer side surface 90 f of the lower bone32 f. To effect rotation of the wedge member 44 f, a suitable tool isinserted into a socket 140 f. Force is transmitted through the tool tothe wedge member 44 f urging the wedge member 44 f to rotate in aclockwise direction from the position shown in FIG. 18 to the positionshown in FIG. 19.

Upon initial application of the force to the wedge member 44 f urgingthe wedge member to rotate in a clockwise direction (as viewed in FIG.18), the pivot end portion 150 f of the wedge member 44 f is pressedagainst the outer side surface 90 f of the lower bone 32 f. At the sametime, the side portion 134 f of the wedge member 44 f begins to slidealong the outer side surface 88 f on the upper bone 30 f.

Continued application of force (torque) to the wedge member 44 f resultsin the wedge member pivoting about an axis which extends through alocation where the end portion 150 f of the wedge member 44 f engagesthe outer side surface 90 f on the lower bone 32 f. As the wedge member44 f pivots about the end portion 150 f, the arcuate nose portion 128 fmoves into engagement with and slides along the outer side surface 88 fon the upper bone 30 f. As the wedge member 44 f approaches theorientation shown in FIG. 19, the joint 34 f is expanded and the spatialrelationship between the upper and lower bones 30 f and 32 f is changedwith a resulting change in the angular orientation of the upper andlower bones relative to each other.

When the wedge member 44 f reaches the orientation shown in FIG. 19, thejoint 34 f has been expanded to the maximum extent possible by the wedgemember. The wedge member 44 f is then connected with the upper and lowerbones 30 f and 32 f by suitable fasteners. The fasteners may extendthrough mounting tabs, similar to the mounting tabs 144 and 146illustrated in FIG. 16 or the fasteners may extend through the wedgemember in the manner illustrated schematically in FIG. 17. Of course,the wedge member 44 f could be held in the upright (as viewed in FIG.19) orientation in any one of many different manners by a suitablefastener arrangement.

Although only a single wedge member 44 f has been shown in FIGS. 18-20,a plurality of the wedge members 44 f could be used to expand the joint34 f and to transmit force between the bones 30 f and 32 f. Whether asingle wedge member 44 f or a plurality of wedge members 44 f are usedto expand the joint, the joint may be packed with bone growth promotingmaterial.

Screw Type Wedge Member

In the embodiment of the invention illustrated in FIGS. 12-16, the wedgemember 44 d has a relatively smooth outer side surface 126. In theembodiment of the invention illustrated in FIGS. 21 and 22, the wedgemember has a configuration similar to the configuration of a screw andhas a irregular outer side surface. Since the embodiment of theinvention illustrated in FIGS. 21 and 22 is generally similar to theembodiments of the invention illustrated in FIGS. 12-20, similarnumerals will be utilized to designate similar components, the suffixletter “g” being associated with the numerals of FIGS. 21 and 22 toavoid confusion.

An upper bone 30 g is connected with a lower bone 32 g in a patient'sbody at a joint 34 g. It should be understood that the joint 34 g hasbeen illustrated schematically in FIG. 21 and may be any joint in apatient's body. A rigid wedge member 44 g is utilized to change thespatial relationship between the upper and lower bones 30 g and 32 g.The wedge member 44 g is effective to expand at least a portion of thejoint 34 g when the wedge member 44 g is inserted into the joint 34 g.

The wedge member 44 g has a thick end portion 50 g and a thin endportion 52 g. The wedge member 44 g has an overall conicalconfiguration. An external thread convolution 160 is formed on the wedgemember 44 g. The external thread convolution 160 has a spiralconfiguration and extends from the thick end portion 50 g to the thinend portion 52 g of the wedge member 44 g.

Although the external thread convolution 160 could have many differentconfigurations, the illustrated thread convolution has generallyV-shaped crests and roots. The general configuration of the externalthread convolution 160 is an American National Form Screw Thread and hasa pitch cone with an angle of between five degrees and twenty degrees.Although one specific external thread convolution has been illustratedand described herein, it should be understood that the external threadconvolution 160 could have a configuration of any one of many differentknown thread convolutions. It is believed that it may be desired to useknown bone screw thread configurations for the configuration of theexternal thread convolution 160.

The rigid wedge member 44 g may be formed of metal, ceramic, human oranimal bone, or suitable polymeric materials. It is believed that itwill be desirable to form the wedge member 44 g of a material which issufficiently rigid to withstand the forces transmitted between the upperand lower bones 30 g and 32 g. If desired, the wedge member 44 g may beformed of a porous material having openings through which bone may grow.It is believed that it may be desired to coat the wedge member 44 g witha bone growth promoting material.

When the wedge member 44 g is to be utilized to change the spatialrelationship between the upper and lower bones 30 g and 32 g, the thinend portion 52 g of the wedge member 44 g is pressed into the joint 34 gbetween the upper and lower bones 30 g and 32 g. The wedge member 44 gis then rotated about its longitudinal central axis 120 g. A hexagonalrecess 140 g is provided in the wedge member 44 g to facilitate thetransmission of force from a suitable tool to the wedge member 44 g.

As the wedge member 44 g is rotated through a plurality of revolutionsabout its longitudinal central axis 120 g, the external threadconvolution 160 g engages the upper and lower bones 30 g and 32 g. Asthe wedge member 44 g is rotated about its longitudinal central 120 g,the external thread convolution 160 engages the upper and lower bones 30g and 32 g and pulls the wedge member into the joint 34 g. As thisoccurs, the joint 34 g is expanded and the spatial relationship betweenthe upper and lower bones 30 g and 32 g is changed.

Once the wedge member 44 g has moved into the joint 34 g and the spatialrelationship between the upper and lower bones 30 g and 32 g has beenchanged, the joint 34 g may be packed with bone growth promotingmaterials and/or bone chips. It is contemplated that various known bonemorphogenic proteins may be used with other osteoinductive materials toinduce bone growth in the joint 34 g. Although only a single wedgemember 44 g is illustrated in FIG. 21, a plurality of wedge members maybe used if desired.

Bone Fitting Wedge Member

In the embodiments of the invention illustrated in FIGS. 1-11, the wedgemembers have flat upper and lower major side surfaces 54 and 56 (FIG.6). In the embodiment of the invention illustrated in FIGS. 23 and 24,the wedge member has nonlinear side surfaces which have been shaped tocorrespond to the configuration of end portions of the bone at a jointbetween the bones. Since the embodiment of the invention illustrated inFIGS. 23 and 24 is generally similar to the embodiments of the inventionillustrated in FIGS. 1-11, similar numerals will be utilized todesignate similar components, the suffix letter “h” being associatedwith the numerals of FIG. 9 to avoid confusion.

Upper and lower bones 30 h and 32 h are interconnected at a joint 34 h.The joint 34 h is a schematic representation of any one of many jointsin a patient's body. The joint 34 h may be in a patient's wrist, ankle,hand, foot, back, or other portion of the patient's body.

When the spatial relationship between the upper and lower bones 30 h and32 h is to be changed, a wedge member 44 h is moved into the joint 34 h.The wedge member 44 h is moved into the joint with a thick end portion50 h of the wedge member trailing and a thin end portion 52 h of thewedge member leading. As the wedge member 44 h is pressed into the joint34 h, upper and lower major side surfaces 54 h and 56 h are pressedagainst outer side surfaces 88 h and 90 h on the upper and lower bones30 h and 32 h. This results in expansion of the joint 34 h in the mannerpreviously described in conjunction with the embodiments of theinvention illustrated in FIGS. 1-11.

In accordance with a feature of this embodiment of the invention, theupper and lower major side surfaces 54 h and 56 h on the wedge member 44h are configured to match the configuration of the outer side surfaces88 h and 90 h on the upper and lower bones 30 h and 32 h, in the mannerillustrated schematically in FIG. 24. By having the upper and lowermajor side surfaces 54 h and 56 h configured to match the configurationof the outer side surfaces 88 h and 90 h on the upper and lower bones 30h and 32 h, the wedge member 44 h is firmly seated against the bone andheld against sidewise (as viewed in FIG. 24) movement relative to thebones. The arcuate configuration of the upper and lower major sidesurfaces 54 h and 56 h on the wedge member 44 h extends from the thickend 50 h of the wedge member 44 h to the thin end 52 h of the wedgemember.

In the embodiment of the invention illustrated in FIG. 24, the wedgemember 44 h is formed of a rigid porous material having an open cellconstruction. A compartment or cavity 100 h in the wedge member 44 hholds bone growth inducing materials 110 h. The bone growth inducingmaterials 110 h may include bone morphogenic proteins and otherosteoinductive materials. The joint 34 h may be packed with bone growthpromoting materials and/or bone chips.

The wedge member 44 h is fixedly connected to the upper and lower bones30 h and 32 h by suitable fasteners (not shown). The wedge member 44 hmay be connected with the upper and lower bones 30 h and 32 h by screwscorresponding to the screws 70 and 72 of FIG. 8. Alternatively, thewedge member 44 h may be connected with the upper and lower bone 30 hand 32 h by screws which extends through mounting tabs, corresponding tothe mounting tabs 144 and 146 of FIG. 16. If desired, the wedge member44 h may be connected with only the upper bone 30 h or only the lowerbone 32 h.

It is believed that by having the side surfaces 54 h and 56 h configuredto correspond to the configuration of the surfaces 88 h and 090 h on thebones 30 h and 32 h, the joint 34 h will be particularly stable when thejoint has been immobilized by connecting the wedge member 44 h to thebones. Although only a single wedge member 34 h has been illustrated inFIGS. 22 and 24, a plurality of wedge members could be used to expandthe joint. It is believed that the wedge member 44 h may be particularlyadvantageous when vertebrae in a patient's back are to beinterconnected.

Conclusion

In view of the foregoing description it is apparent that a new andimproved method and apparatus is provided to change a spatialrelationship between bones 30 and 32 which are interconnected at a joint34 in a patient's body. When this is to be done, an opening is formed ina portion of the patient's body to expose the joint 34 interconnectingthe bones 30 and 32. One of the bones 30 and 32 is moved relative to theother by expanding at least a portion of the joint 34 with a wedgemember 44. The wedge member 44 is moved into the joint and applies forceagainst the bones 30 and 32. The opening is closed with the wedge member44 still disposed in the joint between the bones. Force is thentransmitted between the bones 30 and 32 through the wedge member 44 tomaintain the joint 34 in an expanded condition.

If the joint 34 is to be flexed after being expanded by the wedge member44, the wedge member may be connected with only one of the bones 30 and32. Alternatively, if the joint 34 is to be immobilized (fused) afterinserting the wedge member 44, the wedge member may be fixedly connectedwith the bones 30 and 32 interconnected at the joint. The wedge member44 may be porous and may be coated with and/or contain bone growthpromoting material.

One embodiment of the wedge member 44 has major side surfaces 54 and 56extending between thick and thin end portions 50 and 52 of the wedgemember. The wedge member 44 is moved into the joint 34 with the thinedge portion 52 leading. As the wedge member 44 is moved into the joint34, the thick trailing end portion 50 of the wedge member expands thejoint.

In another embodiment of the invention, the wedge member 44 d, 44 e, 44f, or 44 g may be rotated relative to the joint. In one embodiment ofthe invention, the wedge member 44 g has a circular cross sectionalconfiguration and has an external thread convolution 160 which extendsfrom a thin leading end 52 g of the wedge member to a thick trailing end50 g of the wedge member. The wedge member 44 g is pressed into thejoint 34 g and rotated to cause the wedge member to expand the joint.

In another embodiment of the invention, the wedge member 44 d, 44 e or44 f has surface areas 134 and 136 which are relatively close togetherand other surface areas 128 and 130 which are relatively far apart. Thewedge member 44 d, 44 e, or 44 f is moved into the joint 34 with thesurface areas 134 and 136 which are close together engaging the adjacentbones 30 and 32. The wedge member 44 d, 44 e or 44 f is then rotated toapply force against the adjacent bones to expand the joint. The wedgemember 44 d or 44 e may be rotated about its central axis 120 to applyforced against the bones 30 and 32 and expand the joint. Alternatively,the wedge member 44 f may be rotated about a location where the wedgemember engages one of the bones.

Regardless of which embodiment of the wedge members 44, 44 a, 44 b, 44c, 44 d, 44 e, 44 f, 44 g or 44 h is selected, the wedge member may beused with any one of the many different bones and joints in a patient'sbody. The wedge member may be utilized at joints in a patient's wrist,ankle, hand, foot, back, or other portions of the patient's body. Theuse of the wedge member may be particularly advantageous when a jointbetween vertebrae in a patient's back is to be immobilized. One or morewedge members may be used to expand a joint to transmit force betweenbones.

What is claimed is:
 1. An implantable device for maintaining an expandedcondition of a vertebral joint between a first vertebra and a secondvertebra, the implantable device comprising: a body including a centrallongitudinal axis, a trailing end portion, a leading end portion, afirst side portion, a second side portion, an upper surface and a lowersurface, the upper surface defining a peripheral edge, a first passageextending through the trailing end portion and the upper surface and asecond passage extending through the trailing end portion and the lowersurface, a bone growth passage extending through the body between theupper surface and the lower surface, the bone growth passage surroundedby the peripheral edge, the bone growth passage includes an open upperend and an open lower end, wherein the open upper end is positioned atthe upper surface, the bone growth passage configured to permit bonegrowth through the body, the central longitudinal axis positionedbetween the upper and lower surfaces of the body and being generallyperpendicular to the bone growth passage, the first passage positionedon a first side of the central longitudinal axis and the second passagepositioned on a second side of the central longitudinal axis, a leadingthickness of the leading end portion being substantially consistent at aleading plane perpendicular to the central longitudinal axis, therebydefining a first leading thickness at the first side portion, a secondleading thickness at the second side portion and a middle leadingthickness between the first and second leading thicknesses, the firstleading thickness, the second leading thickness and the middle leadingthickness being substantially equal, a trailing thickness of thetrailing end portion being substantially consistent at a trailing planeperpendicular to the central longitudinal axis, thereby defining a firsttrailing thickness at the first side portion, a second trailingthickness at the second side portion and a middle trailing thicknessbetween the first and second trailing thicknesses, the first trailingthickness, the second trailing thickness and the middle trailingthickness being substantially equal, the trailing thickness beinggreater than the leading thickness.
 2. The implantable device of claim1, further comprising: a first fastener having a first head and a firstshaft, the first fastener positionable in the first passage; and ansecond fastener having a second head and a second shaft, the secondfastener positionable in the second passage, the first head positionableat least partially in the first passage in a mounted configuration andthe second head positionable at least partially in the second passage inthe mounted configuration.
 3. The implantable device of claim 2, whereinthe first head is positionable in a first countersink proximate atrailing end of the trailing end portion in the mounted configuration,the first shaft is positionable in a first channel in the mountedconfiguration, the second head is positionable in a second countersinkproximate the trailing end in the mounted configuration and the secondshaft is positionable in a second channel in the mounted configuration,the first passage comprised of the first countersink and the firstchannel, the second passage comprised of the second countersink and thesecond channel.
 4. The implantable device of claim 3, wherein the firsthead is positionable entirely within the first countersink in themounted configuration and the second head is positionable entirelywithin the second countersink in the mounted configuration.
 5. Theimplantable device of claim 1, wherein the first passage includes afirst countersink extending from a trailing end of the trailing endportion to a first channel, the first channel extending from the firstcountersink to the upper surface, the second passage includes a secondcountersink extending from the trailing end to a second channel, thesecond channel extending from the second countersink to the lowersurface.
 6. The implantable device of claim 1, wherein the body isconstructed of a material selected from the group consisting of a humanbone material, an animal bone material, a metallic material, a ceramicmaterial and a polymeric material.
 7. The implantable device of claim 1,wherein the body is constructed of a polymeric material.
 8. Theimplantable device of claim 1, wherein the body includes a toolingsocket aligned on the central longitudinal axis.
 9. The implantabledevice of claim 1, wherein a leading end of the leading end portion iscomprised of a blunt end portion.
 10. The implantable device of claim 1,wherein the bone growth passage is packable with bone growth material.11. The implantable device of claim 1, wherein the body includes firstand second side surfaces, the first and second side surfaces beingshaped to correspond to the configuration of end plates of the first andsecond vertebrae at the vertebral joint, respectively.
 12. Theimplantable device of claim 1, wherein the body is coated with amaterial that promotes growth of bone.
 13. The implantable device ofclaim 1, wherein the upper and lower surfaces taper toward each otherfrom the trailing end portion to the leading end portion.
 14. Theimplantable device of claim 1, wherein the upper and lower surfacesdefine an acute angle.
 15. The implantable device of claim 14, whereinthe acute angle is between one and thirty degrees (1-30°) .
 16. Theimplantable device of claim 14, wherein the acute angle is between fiveand twenty degrees (5-20°) .
 17. The implantable device of claim 1,wherein the upper surface defines an upper plane and the lower surfacedefines a lower plane, the first passage extending to the upper planeand the second passage extending to the lower plane.
 18. The implantabledevice of claim 1, further comprising: a first countersink associatedwith the first passage at a trailing end of the trailing end portion;and a second countersink associated with the second passage at atrailing end of the trailing end portion.
 19. The implantable device ofclaim 1, wherein the body is formed of a solid piece of material. 20.The implantable device of claim 1, wherein the body is formed by a pieceof porous material.
 21. The implantable device of claim 1, wherein thebody is formed by a hollow piece of porous material.
 22. An implantabledevice for maintaining an expanded condition of a vertebral jointbetween a first vertebra and a second vertebra, the implantable devicecomprising: a body including a trailing end portion, a leading endportion, a first side, a second side, an upper surface and a lowersurface, a central longitudinal axis extending through the trailing endportion and the leading end portion, the body configured to slide intothe vertebral joint in an insertion direction, the central longitudinalaxis oriented generally parallel to the insertion direction, first andsecond passages formed in the body, the first passage extending throughthe trailing end portion at a first trailing end hole, the secondpassage extending through the trailing end portion at a second trailingend hole, the first trailing end hole and the second trailing end holebeing positioned at opposite sides of the central longitudinal axis, abone growth passage formed in the body having an open upper end at theupper surface and an open lower end at the lower surface, the bonegrowth passage being generally linear and extending generallyperpendicular to the central longitudinal axis, the body having aperipheral edge defined at an intersection of the upper surface with thetrailing end portion, the first side, the second side and the leadingend portion, the peripheral edge surrounding the open upper end, thetrailing end portion having a substantially constant trailing thicknesstaken at a trailing plane that is perpendicular to the centrallongitudinal axis, thereby defining a first trailing thickness at thefirst side, a second trailing thickness at the second side and a middletrailing thickness between the first and second trailing thicknesses,the first trailing thickness, the second trailing thickness and themiddle trailing thickness being substantially equal, the leading endportion having a substantially constant leading thickness taken at aleading plane that is perpendicular to the central longitudinal axis,thereby defining a first leading thickness at the first side and asecond leading thickness at the second side, the first leading thicknessand the second leading thickness being substantially equal, the trailingthickness being greater than the leading thickness, the bone growthpassage configured for packing with bone growth material to facilitatebone growth between the first vertebra and the second vertebra in amounted configuration.
 23. The implantable device of claim 22, furthercomprising: a first fastener having a first head and a first shaft, thefirst fastener positionable in the first passage with the first headproximate the first trailing end hole in the mounted configuration; andan second fastener having a second head and a second shaft, the secondfastener positionable in the second passage with the second headproximate the second trailing end hole in the mounted configuration. 24.The implantable device of claim 23, wherein the first head includes afirst rear surface and the first shaft includes first threads proximatea first front end, the second head includes a second rear surface andthe second shaft includes second threads proximate a second front end,the first rear surface and the second rear surface positionable at atrailing end of the trailing end portion in the mounted configuration.25. The implantable device of claim 23, wherein the first passageincludes a first countersink in the trailing end portion and a firstchannel extending from the first countersink to the upper surface, thesecond passage includes a second countersink in the trailing end portionand a second channel extending from the second countersink to the lowersurface.
 26. The implantable device of claim 25, wherein the first shaftis positionable in the first channel and the second shaft ispositionable in the second channel in the mounted configuration, firstthreads of the first fastener configured to engage hard cortical bone ofthe first vertebra in the mounted configuration, second threads of thesecond fastener configured to engage hard cortical bone of the secondvertebra in the mounted configuration.
 27. The implantable device ofclaim 22, wherein the bone growth material is constructed of a materialselected from the group consisting of a bone morphogenic protein, anapatite composition with collagen, a demineralized bone powder and anosteoinductive material.
 28. The implantable device of claim 22, whereinthe body includes a socket in the trailing end portion aligned with thecentral longitudinal axis.
 29. The implantable device of claim 28,wherein the socket is comprised of a tool socket.
 30. The implantabledevice of claim 28, wherein the socket is comprised of a hexagonalrecess.
 31. The implantable device of claim 22, wherein a leading end ofthe leading end portion is comprised of a thin leading end.
 32. Theimplantable device of claim 31, wherein the thin leading end comes to asharp point.
 33. The implantable device of claim 22, wherein a leadingend of the leading end portion is comprised of a blunt end portion. 34.The implantable device of claim 22, wherein the body is formed of arigid open cell material.
 35. The implantable device of claim 22,wherein the first trailing end hole is horizontally aligned with thesecond trailing end hole.
 36. The implantable device of claim 22,wherein the body is constructed of a polymeric material.
 37. Theimplantable device of claim 22, wherein the first passage is positionedbetween the central longitudinal axis and the first side and the secondpassage is positioned between the central longitudinal axis and thesecond side.
 38. The implantable device of claim 22, wherein the body isformed of a solid piece of material.
 39. The implantable device of claim22, wherein the body is formed by a piece of porous material.
 40. Theimplantable device of claim 1, wherein the upper and lower surfaces areflat.
 41. The implantable device of claim 1, wherein the body includesfirst and second side surfaces, the leading end portion includes aleading end, a first end defined at an intersection of the first sidesurface and the leading end and a second end defined at an intersectionof the second side surface and the leading end, the leading end beingsubstantially straight between the first end and the second end.
 42. Theimplantable device of claim 41, wherein the first and second sidesurfaces are arcuate.
 43. The implantable device of claim 1, wherein theleading end portion has a leading end and the trailing end portion has atrailing end, a body length defined between the trailing end and theleading end and the body having a width, the width being greater thanthe body length.
 44. The implantable device of claim 22, wherein theupper and lower surfaces are flat.
 45. The implantable device of claim22, wherein the body includes first and second side surfaces, theleading end portion includes a leading end, a first end defined at anintersection of the first side surface and the leading end and a secondend defined at an intersection of the second side surface and theleading end, the leading end being substantially straight between thefirst end and the second end.
 46. The implantable device of claim 45,wherein the first and second side surfaces are arcuate.
 47. Theimplantable device of claim 22, wherein the leading end portion has aleading end and the trailing end portion has a trailing end, a bodylength defined between the trailing end and the leading end and the bodyhaving a width, the width being greater than the body length.